First of all, they're not measuring how long the average commute is. They're ranking the cities just by how much travel times increase for vehicles at rush hour vs. non rush hour.

Ottawa ranked high because this percentage increase is high, but there is no analysis of how long the actual commute time is.

Furthermore, because it is based on vehicle GPS devices, it completely ignores non-auto commuting. How long is the average Ottawa commuter's commute (including drivers, transit users, walkers, cyclists) versus other cities? This study doesn't tell us that.